As is known, numerous electronic communications devices are today available, which are able to communicate with other electronic devices by means of techniques of coupling of an inductive or electromagnetic type. In particular, these electronic communications devices are provided with a transmitter circuit and at least one antenna coupled to the transmitter circuit. The transmitter circuit is able to drive the antenna in such a way that it generates an electromagnetic field having at least one electrical characteristic (for example, the amplitude, frequency, or phase) modulated with information to be transmitted. Consequently, other electronic devices that receive this electromagnetic field may demodulate the information transmitted.
Considering a generic electronic transmitter device, which generates a given electromagnetic field at least one operating frequency, and a generic electronic receiver device, which is set at a distance h from the transmitter device and receives the given electromagnetic field, between the electronic transmitter device and the electronic receiver device a communications channel is set up, which may also be obtained via a coupling of a magnetic type. In practice, in the case of magnetic or inductive coupling, the information is transmitted principally thanks to a magnetic field generated by the antenna of the electronic transmitter device, whereas, in the case of electromagnetic transmission, the information is transmitted through the propagation of electromagnetic waves generated by the antenna. Consequently, in the case of magnetic or inductive coupling, it is common to use a single or multiple loop antenna, and in this case the electrical behavior of the antenna is equivalent to that of an inductor. In greater detail, in the case of inductive coupling, the antenna can be equated, to a first approximation, to a reactive element, whereas in the case of electromagnetic transmission, the antenna can be equated, to a first approximation, to a resistive element.
In the present document, reference is made to antennas in general, implying the possibility that, in given conditions (and hence, in given applications), these are equivalent, from a circuit standpoint and to a first approximation, to corresponding inductors.
Once again with reference to electronic communications devices, the antennas considered herein may be of a different type, such as for example patch antennas or gain loop antennas, the latter being also known as “magnetic-dipole antennas” and finding particular use in the field of radio-frequency-identification (RFID) applications. For example, in the case of loop antennas, it may be possible for them to be arranged, within the respective electronic communications devices, in such a way that, in top plan view, they surround, or else are set on top of, the corresponding transmitter circuits. In general, it may in any case be possible that, given an electronic communications device, the respective antenna interferes, in use, with the respective transmitter circuit. In order to reduce the interference, there are known electronic communications devices of the type illustrated in FIG. 1.
In detail, the electronic communications device shown in FIG. 1, which for convenience in what follows will be referred to as “device 1”, comprises: a body of semiconductor material 2, which defines a first top surface 2a and in turn comprises a substrate of semiconductor material possibly set on top of which are one or more epitaxial layers (not shown); a top region 4, which extends on the first top surface 2a of the body of semiconductor material 2, and defines a second top surface 4a; a metal shield 6, which extends on the second top surface 4a; a silicon-oxide layer 8, which extends on the metal shield 6; a plurality of metal turns 10, for example of a circular or polygonal shape, which are coplanar and concentric, extend above, and in contact with, the silicon-oxide layer 8 and form, as a whole, an antenna 12; and a possible protective layer 14, which extends on the silicon-oxide layer 18, and extending within which are the aforementioned metal turns 10.
Yet in greater detail, formed within the body of semiconductor material 2 is an electronic circuit. In addition, the top region 4 may comprise dielectric layers and conductive paths formed by metallizations and vias, which are generally coupled to the body of semiconductor material 2 so as to enable connection of the electronic circuit with the antenna 12, as described below. In particular, in FIG. 1 the metallizations are shown in a qualitative way and are designated by 16. In addition, a first metallization and a second metallization, which are designated, respectively, by 16a and 16b, are coupled to the metal shield 6, respectively, by means of a first vertical metal connection 18a and a second vertical metal connection 18b. In particular, as illustrated qualitatively in FIG. 1, the metal shield 6 may be of a planar type, but may have different shapes, such as, for example, shapes known as “cross-bar pattern”, “halo-ground contact”, “narrow-bar pattern”, “wide-bar pattern”, “solid-ground pattern”, “perforated-ground pattern”, and illustrated in FIGS. 2a-2f, respectively.
Finally, as regards in particular the antenna 12, the metal turns 10 that form it may have different widths, but are in any case in ohmic contact with one another, as shown by way of example in FIG. 3, in such a way that it is possible to define a start terminal 20a and an end terminal 20b of the antenna 12. These start and end terminals 20a, 20b are coupled, respectively, by means of a first metal via 22a and a second metal via 22b, to the metal shield 6. In particular, the first and second metal vias 22a, 22b contact the metal shield 6 at points corresponding, respectively, to the points in which the first and second vertical metal connections 18a, 18b contact in turn the metal shield 6.
From a circuit standpoint, the metal shield 6 may be floating or else coupled to ground. In either case, its function is that of limiting any mutual interference between the antenna 12 and the electronic circuit formed in the body of semiconductor material 2. In addition, the shape assumed by the metal shield 6 may be optimized for limiting, in use, onset of loop currents within the metal shield 6 itself, which in turn could interfere with the behavior of the antenna 12. Further known variants envisage use, in lieu of the metal shield 6, of a polysilicon shield in order to prevent undesirable reflections of the electromagnetic field generated by the antenna 12.
As regards, instead, the first and second metal vias 22a, 22b, as well as the silicon-oxide layer 8 and the possible protective layer 14, they may be designed so as to match the impedance of the antenna 12 with the impedance of the electronic circuit.
In general, the antennas present in electronic communications devices of a known type may be, amongst other things, antennas of a so-called LC type, i.e., formed (from an equivalent-circuit standpoint) by an inductor coupled, either in series or in parallel, to a corresponding capacitor. In this way, the behavior of each antenna may be optimized, in particular as regards the conditions of inductive coupling (also known as resonance conditions), for a respective resonance frequency f, which depends upon the inductance associated with the inductor and the capacitance of the capacitor to which the inductor is coupled, according to the relation LCω2=1, where ω=2πf.
In the present electronic communications devices, there hence arises the problem of obtaining these capacitors with sufficient precision and of connecting them to the respective antennas. In particular, electronic communications devices of the type shown in WO2007/086809, which is incorporated by reference, are known, in which the capacitors, and in particular the electrodes of the capacitors themselves, are arranged underneath the respective metal shields. In particular, these capacitors are integrated in the electronic communications devices, either within the respective bodies of semiconductor material or else within the respective top regions. In either case, this entails an increase of the overall dimensions of the electronic communications devices, and in particular of the area of the electronic communications devices.